This application claims the benefit of the Korean Application No. P2002-20678 filed on Apr. 16, 2002, which is hereby incorporated by reference.
1. Field of the Invention
The present invention relates to cross flow fans, and more particularly, to a cross flow fan with unequal pitches, and an air conditioner fitted with the same.
2. Background of the Related Art
In general, the air conditioner is provided with an indoor unit and an outdoor unit, and the indoor unit is provided with an evaporator and fan fitted therein. The fan serves to draw air from a room, to make the air heat exchange at the evaporator, and to blow the air into the room again.
Of the fans employed in the air conditioners, there are sirocco fans, propeller fans, turbo fans, and cross flow fans, wherein the cross flow fans are mostly employed in the indoor units.
A related art cross flow fan in an air conditioner will be described with reference to the attached drawings.
Referring to FIG. 1, the air conditioner is provided with a casing having an inlet 4 and an outlet 5, an evaporator 1, a rear guide 2, a cross flow fan 10, and a stabilizer 3.
The cross flow fan 10 is fitted among the evaporator 1, the rear guide 2 and the stabilizer 3. The cross flow fan draws air through the inlet 4 and discharges through the outlet 5, and generates a vortex as the cross flow fan is rotated by a motor (not shown).
The evaporator 1 between the inlet 4 and the cross flow fan 10 heat exchanges with the air drawn through the inlet 4. The rear guide 2 in rear of the cross flow fan 10 stabilizes the vortex caused by the cross flow fan, and guides air flow. The stabilizer 3 under the cross flow fan 10 separates an inlet 4 region and an outlet 5 region, and stabilizes the air flow toward the outlet 5.
The cross flow fan 10 will be described in more detail.
Referring to FIG. 2, the cross flow fan 10 is provided with a plurality of blocks 11 joined along a rotation shaft B-Bxe2x80x2 direction. Each block 11 has a plurality of annular rims 13 arranged at equal intervals along a horizontal direction, and a plurality of blades 12 arranged on a side surface of the rim 13 vertical thereto, and along a circumference direction of the rim 13.
Referring to FIG. 3, each blade 12 forms a pitch angle Pn to an adjacent blade 12 with reference to a center of the rim 13. The pitch angle Pn is an angle between two adjacent blades 12, with the center of the rim 13 taken as an apex.
The cross flow fan 10 with equal pitched angles is called as an equal pitched cross flow fan 10. The equal pitched cross flow fan 10, having a good fan balance and a low vibration, and is favorable for mass production, is widely used.
However, variations of a pressure at regular intervals cause noise at a particular frequency. The equal pitched cross flow fan 10 has a regular pressure variation when the equal pitched cross flow fan 10 rotates at a constant speed, owing to the regular intervals of the blades 12, i.e., regular pitch angles Pn. Consequently, a sound pressure becomes higher at the particular frequency to cause unpleasant noise.
It is known that the noise is generated at a Blade Passing Frequency (BPF) defined as the following equation.       f    BPF    =      NZ    60  
Where, xe2x80x98Nxe2x80x99 denotes revolutions per min. and Z denotes a number of blades.
For an example, a measurement of sound pressure levels of a rotating equal pitched cross flow fan 10 with 32 blades provides a result as shown in FIG. 4.
Referring to FIG. 4, it can be noted that there are peaks of the sound pressure at approx. 800 Hz frequency intervals. This implies that the unpleasant noise occurs at regular frequency intervals.
Thus, the related art equal pitched cross flow fan 10 has poor noise characteristics due to the loud rotational frequency noise of the blades 12.
Accordingly, the present invention is directed to a cross flow fan, and an air conditioner fitted with the same that substantially obviates one or more of the problems due to limitations and disadvantages of the related art.
An object of the present invention is to provide a cross flow fan which has a reduced noise and vibration, and an air conditioner fitted with the same.
Additional features and advantages of the invention will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.
To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described, the cross flow fan includes a plurality of annular rims arranged at regular intervals along a horizontal direction, and a plurality of blades on a side surface of the rim vertical thereto, and along a circumference direction of the rim, wherein pitch angles between two adjacent blades are not regular, the pitch angle taking a center of the rim as an apex.
When a number of the blades are 32, the pitch angles of the blades arranged in succession in a clockwise or counter clockwise direction with reference to one of the blades are 12.50xc2x0, 9.22xc2x0, 10.00xc2x0, 12.43xc2x0, 11.14xc2x0, 14.08xc2x0, 8.85xc2x0, 12.19xc2x0, 12.39xc2x0, 9.84xc2x0, 11.21xc2x0, 9.41xc2x0, 14.93xc2x0, 10.96xc2x0, 8.18xc2x0, 11.62xc2x0, 12.91xc2x0, 12.00xc2x0, 11.93xc2x0, 10.18xc2x0, 8.33xc2x0, 12.34xc2x0, 10.00xc2x0, 13.90xc2x0, 9.66xc2x0, 12.18xc2x0, 11.87xc2x0, 12.80xc2x0, 11.11xc2x0, 11.23xc2x0, 8.44xc2x0, and 12.16xc2x0.
If the 32 blades are sloped in a clockwise or counter clockwise direction when seen from the side, the pitch angles of the blades arranged in succession in a clockwise or counter clockwise direction with reference to one of the blades are 12.50xc2x0, 9.22xc2x0, 10.00xc2x0, 12.43xc2x0, 11.14xc2x0, 14.08xc2x0, 8.85xc2x0, 12.19xc2x0, 12.39xc2x0, 9.84xc2x0, 11.21xc2x0, 9.41xc2x0, 14.93xc2x0, 10.96xc2x0, 8.18xc2x0, 11.62xc2x0, 12.91xc2x0, 12.00xc2x0, 11.93xc2x0, 10.18xc2x0, 8.33xc2x0, 12.34xc2x0, 10.00xc2x0, 13.90xc2x0, 9.66xc2x0, 12.18xc2x0, 11.87xc2x0, 12.80xc2x0, 11.11xc2x0, 11.23xc2x0, 8.44xc2x0, and 12.16xc2x0.
When a number of the blades are 35, the pitch angles of the blades arranged in succession in a clockwise or counter clockwise direction with reference to one of the blades are 10.00xc2x0, 10.31xc2x0, 9.20xc2x0, 11.64xc2x0, 10.37xc2x0, 10.67xc2x0, 9.41xc2x0, 12.26xc2x0, 8.36xc2x0, 10.25xc2x0, 11.47xc2x0, 8.27xc2x0, 11.33xc2x0, 11.08xc2x0, 9.36xc2x0, 11.29xc2x0, 7.67xc2x0, 13.44xc2x0, 10.10xc2x0, 9.97xc2x0, 8.08xc2x0, 10.26xc2x0, 13.34xc2x0, 8.33xc2x0, 9.89xc2x0, 10.71xc2x0, 9.54xc2x0, 12.51xc2x0, 7.95xc2x0, 11.76xc2x0, 7.92xc2x0, 13.47xc2x0, 10.81xc2x0, 7.80xc2x0, and 10.87xc2x0.
In another aspect of the present invention, there is provided an air conditioner including a casing having an inlet and an outlet, a cross flow fan for drawing air through the inlet and discharging the air through the outlet, the cross flow fan including a plurality of annular rims arranged at regular intervals along a horizontal direction; and a plurality of blades on a side surface of the rim vertical thereto, and along a circumference direction of the rim, wherein pitch angles between two adjacent blades are not regular, the pitch angle taking a center of the rim as an apex, and an evaporator between the inlet and the cross flow fan for making heat exchange with the air drawn through the inlet.
The air conditioner further includes a rear guide in rear of the cross flow fan for stabilizing a vortex occurred by the cross flow fan, and guiding flow of the air, and/or a stabilizer under the cross flow fan to separate the inlet region and the outlet region, for stabilizing flow of the air moving toward the outlet.
When a number of the blades are 32, the pitch angles of the blades arranged in succession in a clockwise or counter clockwise direction with reference to one of the blades are 12.50xc2x0, 9.22xc2x0, 10.00xc2x0, 12.43xc2x0, 11.14xc2x0, 14.08xc2x0, 8.85xc2x0, 12.19xc2x0, 12.39xc2x0, 9.84xc2x0, 11.21xc2x0, 9.41xc2x0, 14.93xc2x0, 10.96xc2x0, 8.18xc2x0, 11.62xc2x0, 12.91xc2x0, 12.00xc2x0, 11.93xc2x0, 10.18xc2x0, 8.33xc2x0, 12.34xc2x0, 10.00xc2x0, 13.90xc2x0, 9.66xc2x0, 12.18xc2x0, 11.87xc2x0, 12.80xc2x0, 11.11xc2x0, 11.23xc2x0, 8.44xc2x0, and 12.16xc2x0.
If the 32 blades are sloped in a clockwise or counter clockwise direction when seen from the side, the pitch angles of the blades arranged in succession in a clockwise or counter clockwise direction with reference to one of the blades are 12.50xc2x0, 9.22xc2x0, 10.00xc2x0, 12.43xc2x0, 11.14xc2x0, 14.08xc2x0, 8.85xc2x0, 12.19xc2x0, 12.39xc2x0, 9.84xc2x0, 11.21xc2x0, 9.41xc2x0, 14.93xc2x0, 10.96xc2x0, 8.18xc2x0, 11.62xc2x0, 12.91xc2x0, 12.00xc2x0, 11.93xc2x0, 10.18xc2x0, 8.33xc2x0, 12.34xc2x0, 10.00xc2x0, 13.90xc2x0, 9.66xc2x0, 12.18xc2x0, 11.87xc2x0, 12.80xc2x0, 11.11xc2x0, 11.23xc2x0, 8.44xc2x0, and 12.16xc2x0.
When a number of the blades are 35, the pitch angles of the blades arranged in succession in a clockwise or counter clockwise direction with reference to one of the blades are 10.00xc2x0, 10.31xc2x0, 9.20xc2x0, 11.64xc2x0, 10.37xc2x0, 10.67xc2x0, 9.41xc2x0, 12.26xc2x0, 8.36xc2x0, 10.25xc2x0, 11.47xc2x0, 8.27xc2x0, 11.33xc2x0, 11.08xc2x0, 9.36xc2x0, 11.29xc2x0, 7.67xc2x0, 13.44xc2x0, 10.10xc2x0, 9.97xc2x0, 8.08xc2x0, 10.26xc2x0, 13.34xc2x0, 8.33xc2x0, 9.89xc2x0, 10.71xc2x0, 9.54xc2x0, 12.51xc2x0, 7.95xc2x0, 11.76xc2x0, 7.92xc2x0, 13.47xc2x0, 10.81xc2x0, 7.80xc2x0, and 10.87xc2x0.
If the 35 blades are sloped in a clockwise or counter clockwise direction when seen from the side, the pitch angles of the blades arranged in succession in a clockwise or counter clockwise direction with reference to one of the blades are 10.00xc2x0, 10.31xc2x0, 9.20xc2x0, 11.64xc2x0, 10.37xc2x0, 10.67xc2x0, 9.41xc2x0, 12.26xc2x0, 8.36xc2x0, 10.25xc2x0, 11.47xc2x0, 8.27xc2x0, 11.33xc2x0, 11.08xc2x0, 9.36xc2x0, 11.29xc2x0, 7.67xc2x0, 13.44xc2x0, 10.10xc2x0, 9.97xc2x0, 8.08xc2x0, 10.26xc2x0, 13.34xc2x0, 8.33xc2x0,9.89xc2x0, 10.71xc2x0, 9.54xc2x0, 12.51xc2x0, 7.95xc2x0, 11.76xc2x0, 7.92xc2x0, 13.47xc2x0, 10.81xc2x0, 7.80xc2x0, and 10.87xc2x0.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed.